The research for which continued support is requested is addressed to the mammalian forebrain organization in general and to the higher order olfactory connections in particular. The study on the efferent projections of the temporal allocortex in the guinea pig as completed during the last year, and the discovery of well defined projections to the hippocampus and the central amygdaloid nucleus from periamygdaloid- and transitional cortex respectively serves to emphasize the close relation between olfactory and hippocampal mechanisms on one hand and between the olfactory system and the central amygdaloid-bed nucleus of stria terminalis-circuit on the other. Following our description of fiber projections from the olfactory tubercle to the ventral part of the globus pallidus we are currently involved in a detailed light- and electron microscopic study of the cytology and intrinsic organization of the olfactory tubercle. One of the major objectives in this project is to determine to what extent, if any, the olfactooy tubercle is striatal in nature. Further investigations in progress include: 1. The mapping of degeneration following restricted lesions in different parts of primary and secondary olfactory formations in rat, guinea pig and armadillo and 2. The ultrastructural study of cell-degeneration in the olfactory cortex following ipsilateral bulb removals in the rat.